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Questions tagged [digital-communications]

Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.

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1answer
74 views

optical glow fiber for low-tech communication links?

Can cheap "glow" optical fiber (or other inexpensive materials such as aquarium air tubing, etc.) be used for low-tech low-speed optical communications using just simple discrete components, such as ...
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2answers
2k views

RX vs TX operation in Software UART

I am short of 1 UART in my MCU. I needed 4 but so far what I have found suitable is an MCU that has 3 UARTs in it, STM32F103. So the 4th one I will have to implement in SW. Each of my individual ...
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0answers
78 views

CAN Sniffing - is my approach flawed? [on hold]

I'm working on an automotive project to sniff CAN data and reverse engineer PIDs. The project is based on a ChipKit Max32 & Network Shield - chosen for its dual channel CAN controllers. The idea ...
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25 views

RSS/RSSI Applications? [closed]

What are the applications of knowing RSSI as an absolute value or as a relative value? I know the importance of this in estimating distance for Indoor localization, but, what else can you think of? ...
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0answers
54 views

Trouble connecting to temperature controller using MODBUS,RS485 and MATLAB

I am trying to communicate with a temperaturature controller ATR-401 using MATLAB but i am having trouble just connecting to it and reading temperature data.I have set baud rate, data bits, parity and ...
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0answers
24 views

User Bandwidth and Throughput in mmWave?

I would like to calculate the maximum achievable throughput for a user in downlink communication in the mmWave band. I know that the Shannon's Capacity equation can be used for this, but to use it I ...
2
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1answer
103 views

What is this radiation coming from my phone?

I've built myself a crude EMI probe: I then pointed it at the top part of my phone when the phone was powered on, and I saw the following waveforms on my scope. First off, there are spikes every ...
0
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1answer
56 views

Shannon - Hartley Theorem

Let's consider the Shannon - Hartley formula for the channel capacity \$C\$: $$C = B \log_2 (1 + S/N)$$ I have two doubts about it: 1) is it correct for TDMA, FDMA, or CDMA? And why? 2) Can a ...
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1answer
54 views

Energy of a complex exponential signal

Noob question here. Why would the term \$j2\pi t\$ not have any effect on the energy of the signal?
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0answers
17 views

PAPR (Peak to average power ratio) of OFDM signals

Will the PAPR of an OFDM signal using QPSK modulation on its subcarriers be different than the PAPR of an OFDM signal using QAM256 on its subcarriers? assuming the same number of subcarriers
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27 views

Setting up parameters for generating QAM signals

I am trying to simulate multiple baseband QAM signals for random data at varying power levels, data-rate, carrier frequency, and modulation order using MATLAB. Here is how I set up the parameters: <...
0
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0answers
40 views

Two-way communication between esp32s

I am planning a circuit that requires two-way communication between one esp32 and 3 others. I want to use a master/slave architecture as shown here: They need to be able to communicated via hardware, ...
0
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1answer
53 views

8085 MPU; Stepping through an instruction (Timing diagrams)

Let me write the steps of ADD B, as I've understood it till now. T0: ALE goes high Memory location(say \$2000_h\$) is taken from Program Counter to Memory Address Register(which points to the ...
2
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0answers
92 views

Vanishing of Gibbs Phenomenon in MatLab

I was trying to represent a square wave with its Fourier series in Matlab. But as I increased the number of terms in Fourier series expression, the Gibbs phenomenon vanished and the edges of the ...
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0answers
38 views

Need help in computing the evolution of symbol error rate for uncoded OOK scheme over fading channels

I am trying to reproduce the results exhibited in Fig. 1. in the reference, i.e., "Error performance of coded FSO links in turbulent atmosphere modeled by gamma-gamma distributions" linked to (https://...
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1answer
54 views

Can anybody explain to me how to solve such questions? Constellation Diagram [closed]

i'm not able to proceed with such questions. If someone could explain how to solve such questions, would be a big help. Thanks.
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0answers
56 views

GBE (Gigabit Ethernet) Magnetic Coils Connection Order

I am designing a MEZ PCB and I need to connect the GBE coils to the assigned pins of single board computer's MEZ connector. My trouble is I do not want to use any more via for this connections. Hence, ...
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2answers
59 views

Preventing audio feedback in an underwater multiway intercom

I'm trying to transmit data(bytes) from a speaker (out) to microphone (in) via an FM modulated link. Now I have the problem that both will be used simultaneously (full duplex) and next to each other (...
1
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2answers
78 views

Is there a method to get the carrier from the recieved QPSK signal?

If we have given a signal and we know that is a modulated QPSK signal, can we recover the carrier if we know the carrier frequency fc. Edit: A clarification, I do not have to do it in hardware, a ...
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0answers
19 views

How to perform multiplication at the time series level for chirp signals

As the title said: How to perform multiplication at the time series level for chirp signals? In LoRa modulation, when received a chirp modulated signal, to demodulate it, LoRa will first multiple the ...
25
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13answers
4k views

Examples of fluid (including air) being used to transmit digital data? [closed]

We usually use electrons to communicate data across wires, and sometimes we use light also. Does anyone know of real world example systems that use fluids (including air) to do this, and the ...
0
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1answer
46 views

What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal?

What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal? Shouldn't it be infinity as short periods of sinusoids are used to depict 1 and 0 to depict 0?
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26 views

CAN Transciever kbps to Hz at TXD Pin

I am new to the CAN Bus and have designed an application example. The Transceiver I have chosen is TJA1044Gx. The transceiver data sheet says : I want to know if I have only Transceiver, Analog ...
0
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2answers
69 views

Can we band pass filter QPSK signal?

Consider we have QPSK signal with carrier frequency 10kHz. Generally, we demodulate or use matched filter on the the QPSK signal and recover the transmitted bit or the symbols. If the QPSk signal is ...
1
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0answers
8 views

How is n_pucch_2 in rrc layer computed

In LTE network I know that n_pucch_2 is used to indicate the resource index for pucch format 2/2a/2b. And I know its value is defined in higher layer. But how is the value computed and defined in the ...
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1answer
39 views

What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?

Consider we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take sampls from the received signal. So what is the minimum sampling ...
0
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1answer
31 views

Machine comms troubleshooting

While this may be suited for an automotive section I believe my question is better suited to this forum. I'm having OBD II comms issues and have a run a similar troubleshooting process to what's ...
0
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1answer
66 views

JSON for GSM Comm on STM32

I am making a remote monitoring system using STM32F1 MCU in which there are few digital and analog sensors attached and I would send their readings to a remote server periodically. Can I use JSON ...
3
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0answers
141 views

Strange I2C communication

I am currently trying to test the SHT3x series humidity sensors by Senserion. I have their EK-H4 evaluation kit to get data from the sensors. I can plug in the sesnsors provided with the kit, and all ...
0
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2answers
41 views

1-wire differentiate read from write

I've been reading documentation on 1-wire and I think I'm having a brainfart. How does the slave differentiate a read slot from a write slot? reference: https://www.maximintegrated.com/en/app-notes/...
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0answers
143 views

How to Low-Pass PDM Output Data

I have a PDM-Mems Microphone which provides me with 101010 data, the Microphone has a Clock of 3Mhz. I read the manual about how PDM is generated, but I haven't worked with digital filters yet and in ...
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1answer
36 views

Pairing vs Master-slave between BT Module to BT Module

If I take two identical BT modules, for example HC05 or HC06 then is it possible to pair the two modules with each other or is it like you need 1 master and 1 slave module for pairing? Edit: Now I ...
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1answer
73 views

Bluetooth vs BT Beacon [closed]

While trying to understand how BT devices work I came across another related term "BT Beacon". Is it same as BT communication or if a device is termed as BT beacon then it would have some specific ...
0
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0answers
49 views

What is the fieldbus for Unitronics PLC?

I am currently investigating the inner behavior of a PLC of the brand Unitronics. I identified several bus for the communication with actuators, other PLCs, etc (like Modbus or CANbus) One thing I ...
0
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0answers
10 views

finding the minimal length of a broadcasting frame in a channel(CSMA/CD)

i am unsure about this question. would appreciate your assistance with it. in the following CSMA/CD network with cable length L and propagation T. assuming that the signal is not decreasing and there'...
0
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2answers
87 views

Does direct GPIO communication between 2 microcontrollers requires pull up/down

If I want to use GPIO pins of two microcontrolles as a mean of simple communication (e.g. reporting an event by sending 1 or 0), Do I need to enable internal pull up or pull down resistors on any of ...
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0answers
88 views

Probing LPC bus with an FPGA yields gibberish — wiring problem?

I'm trying to repeat the TPM key dumping experiment by Pulse Security using a motherboard with Secure Boot and the same TPM1.2 chip onboard, equipped with Windows 8. However, when I connect the FPGA ...
0
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1answer
59 views

Finding the overhead and distance of an unknown code based on message making algorithm

for an information word M with m bits that is coded as following: M is coded into a word A using an unknown code that allows detection of not more than one error. the code word is the word obtained ...
0
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1answer
16 views

loading multiple shift registers from few pins

We want to load two 32 bit data shift registers without concatenating them using 4 control lines (SI1, SI2 clock, latch). It can be done by bit banging but can it be done using SPIs using only 4 lines?...
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0answers
25 views

Find Bit Error Rate and Eb/N0?

I have read about Bit Error Rate and Eb/N0 to find out how can I generate them. I understand BER but what confused me is Eb/N0. How can I find Eb/N0 values and the corresponding BER values. I have ...
1
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1answer
77 views

Signal placement in flat ribbon cable, FPC or FFC with digital and power signals

I want to interface different boards with FPC/FFC or ribbon cable and I was wondering about the placement of the signals in the cable. I plan to have a 39 signals FPC with : 1 SPI bus (SCK, MOSI, ...
0
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1answer
53 views

Visualise a bit pattern

My objective is to send a bit pattern of 1000 bits from one microcontroller (PIC or Atmel) to another one using the SPI method. How can I visualize the bit pattern so I can find the errors of ...
1
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1answer
39 views

Source generator for Satellite Tuner input

I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the ...
1
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1answer
44 views

What is the effect of redundancy coding on the bit error rate?

If I have a channel with bit error rate BER = \$10^{-3}\$ after modulation, but this is too high so I decide to add repetition coding. With 2 code words and block length of 3 such that I have a ...
0
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3answers
94 views

Choosing best bus and protocol for ~128 clients over the wire

I am up to design system with ~128 MCUs communicating to one MCU master. Communication will be bidirectional. Data will be mostly sensor reads, but I plan to use the bus also as communication method ...
0
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1answer
106 views

How do I stop signal looping with I/O port in this communication system

I am still a student. When I am designing communication system I am facing this problem: As shown in the figure I need to communicate with Master and Slave. But Master and Slave have single I/O port ...
2
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3answers
185 views

How is companding different from pre-emphasis and de-emphasis?

What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which ...
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1answer
303 views

Signed and unsigned numbers in verilog

I understand the concept of fixed point and multiplying signed with unsigned by sign extension the unsigned number with 1 bit of '0' so it will be signed always positive number, But my question If I ...
0
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1answer
97 views

UART Transmit issue in VHDL

I'm working on a UART transmit process (uart_transmit) in VHDL (115200 baud, 8 data bits, 1 stop bit and no parity). I need the transmit line ...
0
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1answer
191 views

Are horizontal and vertical back porches required for digital video, and if so, why?

The necessity of vertical and horizontal front and back porches in analog video seem fairly intuitive to me, but why are they necessary for digital video at all? In this LCD module data sheet and this ...